Electrical fans, although introduced more than 100 years ago, are still a viable alternative to contemporary air conditioners. In today's more demanding market, however, fan makers find that to maintain their competitiveness, they must offer systems which both have a wider range of features, and which retain traditional system low cost and simplicity.
While air conditioners have become a standard feature of contemporary life, they, nonetheless, have many drawbacks. They are costly to purchase and install, are expensive to operate and have complicated constructions which can be difficult to repair. Additionally, many people find the low temperature settings of air conditioners, typical of most usage, uncomfortable, particularly when moving between places which are air conditioned and those which are not. Yet further, many find the absence of fresh air associated with air conditioned environments both unnatural and unpleasant.
As a result, electric fans, first introduced in the early 1880's, have retained their popularity. Common electric room fans are typically on the order of one tenth the cost of room air conditioners, require no installation other than placement in a convenient location; e.g., floor, table, window, require minimal cost to operate and are exceedingly reliable because of their simplicity. Additionally, they are capable of producing comforting currents of natural air which avoid stark contrasts in temperature.
However, to broaden the appeal of their products, fan makers find they are required to offer a wider range of features; e.g., modes of operation, while maintaining low cost and simplicity. Since consumers seek value when considering whether or not to substitute a fan system either partially or wholly for air conditioners, they look for products that can do the most for them at the lowest price. Therefore, in addition to performing the conventional function of moving air, fan makers have proposed systems which also operate as ventilators; i.e., replace stale air with fresh air; as for example, by supplying fresh external air and exhausting stale air, important where room air may be particularly foul because of tobacco smoke or cooking odors, etc., or by circulating room, ambient air through a filtering means to refresh it, as where conservation of ambient temperature is important.
The problem has been that such enhancement of function; i.e., addition of modes of operation, have not been without the addition of undesirable complexity and cost. Further, due to the inconsistent nature of elements required for the various modes of operation, systems thus far proposed have been unable to combine a variety of such functions in a single, low cost, multi-purpose unit. Particularly, systems which ventilate by taking in fresh air and exhausting stale air have not included means for filtering and circulating ambient air. Nor have systems designed to filter and circulate ambient air, typically portable units, included the more elaborate features found in fix mounted systems for ventilating by taking in fresh air and exhausting stale air. Further, the absence of added features in portable systems is particularly noticeable. The problem here is that because portable units stress low cost it is particularly difficult to add features to them without complicating their design and rendering them more expensive and less competitive.
For example, while portable fan ventilators have been proposed that can alternately supply external fresh air or exhaust stale air; i.e., reversible, portable fans, their designs are unable to filter and circulate ambient air or to simultaneously supply fresh air and exhaust stale air. U.S. Pat. No. 3,385,516 to W. A. Omohundro in an illustration. While primarily directed to an arrangement of fan hub and motor, the patent describes a portable fan unit having a single fan designed to either move air in one direction or the other; i.e., used either within the room to move air, or at a window to either supply fresh air or exhaust stale air. The unit, however, lacks any filter means and, therefore, is not capable of ventilation by circulating ambient air. As a result, the design sacrifices either temperature conservation for air purity, or vice versa, being able to address one concern or the other, but not both. Further, because the unit uses a single fan, it can not simultaneously supply fresh air and exhaust stale air. This potentially compromises air quality by limiting the rate stale is exchanged for fresh air, particularly a problem where room ventilation is limited to use of the fan alone.
While other fan ventilators have been proposed that are capable of simultaneously supplying external fresh air and exhausting stale air, they, however, are of intricate design, lack the ability to circulate and filter ambient air and are not portable to permit location as desired. An illustration of this type design is given in U.S. Pat. No. 2,152,614 to A. R. Younger. The Younger ventilator, while able to simultaneously take in fresh air and exhaust stale air, requires an elaborate combination of a single motor and dual, opposed fan blades, together with interwoven supply and exhaust channels. Additionally, the design expressly avoids communication between the supply and exhaust channels and fails to consider use of any filtering means. As a result, it is unable to ventilate by filtering circulated ambient air and, thereby, declines conservation of air temperature, Further, the design contemplates fixed installation in a wall or window, and is not transportable.
A yet further ventilator type is described in U.S. Pat. No. 2,850,598 to H. G. Boehm. In his specification, Boehm proposes a fan system that ventilates by circulating ambient air through a filter element, The system features a fan blade and drive motor axially disposed relative to a cylindrical filter element for drawing room air through the filter to refresh it and, thereafter, return it to the room. The system, however, is unable to supply fresh air from outside the room or to exhaust stale air to a region outside the room, thus potentially comprising air purity in heavily air fouled situations.
Continuing, fan ventilators have also been proposed which more closely approach the objective. But they too, for reasons of complexity and omitted features, fall short. U.S. Pat. No. 4,509,411 to E. T. Martin proposes a fan ventilator capable of adjustable supplying fresh air, exhausting stale air and mixing them with circulated ambient air. The system features two fixed direction fans coupled pneumatically by a manifold that can be adjustable split to let out varying amounts of exhausted stale air and let in varying amounts of fresh air to mix with circulating ambient air. While the system has the advantage of conserving the temperature (hot or cold) by circulating at least a portion of the ambient air, the system, nonetheless, fails to consider use of filtering means to refresh the circulated air, is of complicated design by virtue of the adjustable manifold and by its nature is intended to be fixed mounted, not portable.
Still further, while there are fan ventilators that contemplate the supply of filtred fresh air, exhaust of stale air and some circulation of ambient air, again, these systems fail to attain the objectives sought here. Particularly, U.S. Pat. No. 3,363,531 to H. Kohlmeyer et al. describes a fan ventilator for fixed mounting in walls such as those of a barn. The system, features a fan for drawing external fresh air through a port and channel located in the barn wall, and exhausting barn air externally through another port and channel in the barn wall. In accordance with the described system, a flap valve is provided between the supply and exhaust channels to enable controlled circulation of exhaust air with incoming fresh air. Still further, the design contemplates use of filtering means at the supply port, but, however, fails to consider or propose filtering of the circulated air at the flap valve. Additionally the design is large and cumbersome, being intended for fixed mounting and not transport.
Thus while fan systems have been with us for a long while, and offered in a variety of forms, no one design has been able to combine the various features in a single, low cost multi-purpose unit.